Nanowires are man-made structures on the scale of nanometers that are used in miniature electronic circuits such as amplifiers and transistors. It is known in the art to functionalize these nanowires so that they are able to detect the presence of a certain molecule in a volume of air or liquid. Typically, these devices, which are also known by the term “lab-on-a-chip,” have nanowires that have been treated so that the resistance to electrical current through them changes when the nanowire is in the presence of the molecule of interest. When the resistance in the nanowire changes, the voltage change across the nanowire can easily be measured and thus the substance of interest can be detected. Mass production of single functional nanowires of uniform diameter has proven to be extremely difficult, however, because the prior art methods of production result in bundled nanowires of non-uniform width and quality. Uniformity of diameter is important so that devices all start with the same initial conductance.
One important use for these functionalized or surface modified nanowires with antibodies is to place them across channels through which fluids to be analyzed can pass. These so-called microfluidic devices have been designed to detect the presence of a wide range of chemicals, biological triggers and other biomarkers.
Cardiovascular disease claims about thirty-two lives per second, world wide, and in the United States, claims two lives per minute according to published statistics. B-type natriuretic peptide (BNP) is a biomarker for Myocardial Infarction and is used in hospitals and emergency rooms (ER) to monitor Cardiovascular disease (CVD) patients. BNP is a biomarker for myocardial infarction because it is well-known that when a patient's heart failure symptoms begin or worsen, the ventricles in the heart secrete BNP, causing an elevated level of the marker in the blood. Generally speaking, the greater the BNP level in the blood, the more severe the condition.
This correlation between heart failure and BNP is well known and it is routine to test for BNP in the blood of a patient presenting in an emergency room complaining of shortness of breath or some other symptom of heart failure, especially when there is a suggestive history of this type of problem. The drawback to this emergency room test, however, is that instead of predicting a heart problem, it is relegated to confirming the source of symptoms the patient is complaining of in the emergency room—well after the onset of the negative heart event.
What is needed is a way to monitor this biomarker on a regular basis for those at an elevated risk of heart failure so that a negative event can be caught much earlier, preferably outside the health care system setting, resulting in better care at a lower overall cost due to reduced incidence of hospitalization. While BNP levels are generally measured in hospitals and ERs, there is no system offering high sensitivity, extreme selectivity and low cost for the detection of BNP that can be used for a CVD patient to test BNP levels at home.